Kneading Conference West – 2011!

Baking Fundamentals - Core Concepts!Lee Glass!

Course overview!!! Fundamentals:!

!! Introduction!!! Starch!!! Proteins!!! Yeast!!! Salt!!! Mixing!!! Fermentation!!! Baking!

History!

!! Post-World War II!!! US: Prosperity!

!!Levittown - a home for everybody!!!More rural electrification: lots more things to do!!!Chevrolet - See the USA in your Chevrolet !!!Supermarkets replaced neighborhood stores!!!Newer is better!

Post-WW II Prosperity - US!!! Chemistry - cornerstone of prosperity!

!! Monsanto: Better living through chemistry !!! Pittsburgh Paint & Glass: grape flavoring!!! Cereal chemists -- the biochemistry of grains!!! Age of the atom -- plant research with radiation!!! Food chemists - bringing it all home!

!! Wonder Bread®!!! Holsum Bread®!!! Etc.!

Post-WW II: Europe!

!! Food and money were scarce following WW II (Rationing ended in England in 1952)!

!! Important that production minimize costs and maximize output!

!! Adoption of techniques being popularized in the US!

!! Result: French Wonder Bread® !

Artisan Breads!!! A tradition with some long-established

bakeries: e.g. Boudin (since 1849, in SFO)!!! Created by others who sought to provide

artisan products: e.g. Acme Bakery, by Steve Sullivan, in 1983; Artisan Bakers, by Craig Ponsford, in 1992!

!! Now a major market: e.g. Essential, Macrina, Le Panzanella, Grand Central, and others, all in Seattle!

Science in Breadmaking!!! Chorleywood Process: It s all science!

!! Flour to packaged loaf in ~ 3.5 hours!!! Mixing measured by energy input in kWh, not dough

characteristics!!! Negative pressure proofing!!! Decreased partial pressure nitrogen compared to air!

!! Artisan bread: little emphasis on science!!! Most texts emphasize how to , not why !!! No standardized national basic instruction for bakers!

Questions!

!! Can we as artisan bakers use knowledge of the science underlying breadmaking to:!!! Help our breads develop!

!!Maximum flavor!!!The desired crumb structure and consistency!!!The crust we are seeking!!!The color we want our loaves to have?!

!! Help manage our doughs?!

Goals of this segment!!! Explore basic science knowledge related to!

!! Flour!!! Yeast!!! Salt!!! Water!!! Mixing!!! Fermentation!!! Baking!

!! Explore practical correlates of that knowledge!

Goals of key players!

!! Goal of wheat: make more wheat!!! Goal of yeast: make more yeast!!! Goal of lactobacilli: make more lactobacilli!!! Goal of baker: make bread!!! Key challenge for baker: orchestrate a

symphony for discordant instruments!

Flour!!! Starch!

!! Long chains ( polymers ) of glucose molecules!!! Amylose = straight chains!

!! About 25% of wheat starch!!! Amylopectin = branched chains!

!! 1 branch for about each 30 or more glucose molecules!!! About 75% of wheat starch!

!! Starch granules are compact clusters of amylose and amylopectin!

!! Starch granules absorb little water at room temp!!! With heat, starch granules can bind large quantities of

water!

Starch!!! Some roles of starch in bread making!

!! Absorbs huge amounts of water during baking!

!! Stabilizes the crumb!!! Its ultimate breakdown product (glucose) has

a major effect on crust color and flavor!!! Its ultimate breakdown product (glucose)

feeds yeast (and bacteria, if any)!

Starch!

!! Wheat consists of ~60% starch!!! Role of starch for wheat: feed developing

seedling. !!! Seedlings, yeast & lactobacilli cannot eat

starch!!! Starch must be converted to smaller

components to be a useful energy source!!! Conversion is facilitated by enzymes!

Starch - Interaction with proteins!

!! Enzymes are proteins that facilitate chemical reactions, without themselves changing!

!! Enzymes work within narrow temperature and pH ranges!

!! Enzymes are extraordinarily specific in what they do!

Starch - Interaction with Proteins!

!! Amylase!!! Beta: normally present in substantial amounts

the wheat kernel!!! Alpha: presence depends upon growing

conditions, weather near time of harvest, and other factors.!!!Barley is sprouted, dried, powdered, and added at

the mill if necessary in order to have appropriate levels of alpha-amylase in the milled product.!

Starch - Interaction with Proteins!

!! Amylase - two major forms, with some variation. !!! Alpha amylase:!

!!Can cut straight chains almost anywhere!!!Cannot cut branch points!

!! Beta amylase:!!!Starts at one end of a chain, and chops off 2 links at

a time.!!!Can cut at branch points.!

!

Starch - Amylase!

!! Temperature data for wheat amylases:!!! Alpha-amylase!

!! Optimum range: 60° C to 70 ° C!!! Thermal inactivation: 70 ° C to 85 ° C!

!! Beta-amylase!!! Optimum range: ~50 ° C!!! Thermal inactivation: 55 ° C to 75 ° C!

!! Fungal amylase are less heat stable!

Starch - Interaction with Proteins!

!! Amylase activity!!! Measured by falling number !

!!Falling number = number of seconds for a weight to settle through a hot, gelatinized starch mixture!

!!Rationale: as alpha-amylase cuts the starch chains, starch s ability to continue to hold water decreases, viscosity decreases, and the weight falls faster.!

!!The falling time reflects, indirectly, the amount of amylase activity.!

Starch- Interaction with Proteins!

!! Falling number results:!!! Sound wheat: higher than 300!!! Sprout-damaged wheat: below 200!!! IMPORTANT: Falling number may not accurately

reflect flour characteristics when fungal amylase is the source of alpha amylase in the flour being tested. REASON: Fungal amylase is deactivated at a lower temperature than that used in the falling number test.!

Starch - Interaction with Proteins!

!! Products of alpha- and beta-amylase on starch:!

!! Alpha: principally =>!!! 1 sugar (monosaccharide) = glucose!!! 2 linked glucose molecules = maltose!!! Longer chains!

!! Beta: principally =>!!! 2 linked glucose molecules = maltose!

Starch - Granules!

!! Granules:!!! Tight, compact bundles of amylose and

amylopectin!!! Compactness resists effects of amylases!

Starch - Damaged!!! Damaged starch granules:!

!! Present at about 5% to 10% of the starch!!! Have very different qualities than native starch!!! Can absorb water at room temperature!!! Easily attacked by amylase!!! Absorb their own weight in water!!! If present at >10%, dough will be sticky!!! The higher the percentage of damaged starch, the

softer the crumb!!! At high percentages, may cause keyholing !

Proteins!

!! Proteins are chains !!! Each link in the chain is an amino acid!!! The order of the amino acid sequences,

and the characteristics of the amino acids, cause the chains to twist into complex shapes. !

!! The shapes are related to what the proteins do (form relates to function)!

Proteins!

!! Water-insoluble!!! Most important for bakers: gluten proteins:!

!!Gliadins -- low molecular weight storage proteins!!!Glutenins -- hi molecular weight storage proteins!!!Note: storage proteins are found principally in the

endosperm!

Proteins!!! Gliadins!

!!Most extensively studied (to find markers that might correlate with wheat quality)!!!Hundreds of different, distinguishable

gliadin components!!!Gliadins are compact, tightly folded

molecules!!!Relatively stable to temperature challenges!!!Contain the portion of gluten that causes

celiac disease (an immune reaction that damages the small intestine, causing malabsorption problems)!

Proteins!

!! Glutenins!!! Made up of a series of protein subunits that

are cross-linked in a way that produces a broad spectrum of sizes!

!! Huge molecules, compared to the gliadins!!! How these molecules are cross-linked is not

exactly clear.!

Proteins!

!! Gluten structure!!! Clear underlying science (disulfide bonds, etc.)!!! Considerable controversy remains!!! Possible:!

!!Glutenin units link together!!!Gliadin units, singularly or as a polymer, link to

adjacent glutenin units!!!Result: A three-dimensional protein fabric that has

multi-directional extensibility!

Proteins!

!! Gluten correlates of baking quality of flour:!!! 1. The gluten resists breakdown during

mixing!!! 2. The gluten aggregates quickly during rest

and during stretch-and-folds!

Proteins!

!! Flour protein is often expressed as a simple percent: e.g. 11.5%!

!! A percent number tells nothing about!!! The nature of the protein!!! The quality of the protein!!! The characteristics of the dough that might be

made with the flour!

Proteins!

!! Classification - based on solubility!!! About 20% of the proteins are soluble in water!!! The remaining 80% are not. It is in this 80%

that the gluten-forming proteins can be found!!! Note: It is because these proteins do not

dissolve in water, and because bread is made with water, that gluten forms. Were bread made with acid, in which the proteins can be dissolved, gluten would not form.!

Proteins!!! Water-soluble proteins!

!! Include physiologically active proteins:!!! Enzymes, e.g.!

!! Amylases!!! Maltase!

!! Albumins!!! Globulins!

!! Note: physiologically active proteins are found principally in the aleurone layer, and in the germ!

!! The fraction of total wheat protein that is physiologically active depends on factors such as climate, nitrogen availability, season during which wheat grew, etc. !

Proteins!!! Distribution of proteins!

!! Note that the distribution of proteins varies from one part of the kernel to another. (See above.)!!! Implication: the portions of the wheat kernel

blended by the miller to make a given flour may tell more about the flour s protein than may a stated percent:!

!! E.g. absent treatment by the miller, a patent flour may have little enzymatic activity compared to a whole grain flour from the same shipment of wheat kernels.!

Yeast!

!! Saccharomyces cerevisiae!!! Single cell organism that can live with or

without oxygen!!! With oxygen: glucose => CO2 + energy!!! With oxygen: reproduce several times an hour!!! Without oxygen: glucose => CO2 + ethanol !! Without oxygen: no reproduction

Salt!!! Salt has several actions:!

!! Works as an anti-oxidant - Calvel recommends its addition at the beginning of mixing!

!! Salt increases cohesiveness of dough during mixing. (Without salt, dough stays slack.)!

!! Salt decreases fermentation (2% salt reduces fermentation by 20%; 4% => 70% reduction)!

!! Salt makes a beneficial contribution to taste!

Mixing!

!! Mixing - Overview:!!! Homogenizes the ingredients!

!!Disperses dry ingredients!!!Equalizes absorption of liquids!

!! Entraps air in the developing dough!!! Exposes dough components to oxidation!

!!Enhances gluten development!!!May oxidize flavor elements and decrease flavor!

Mixing!

!! Homogeneous mass:!!! Initially, not homogeneous!

!!Water absorption is uneven - first particles to become wet get more water than later particles!

!! Becomes uniform by end of mixing!!!Salt and sugars dissolve!

!! Both may affect yeast activity!!!Fats spread!

!! Affect gluten development!!! Timing of fat addition may be important!

Mixing!!! Entraps air in dough!

!! Gas nuclei -- a critically important concept!!! Bubbles: Pressure resisting expansion = surface tension X 2

divided by bubble radius!!! Mixing atmosphere: in craft bakeries, O2 and N2

!! O2 is consumed immediately !! N2 is poorly soluble, and stays in nuclei !! CO2 diffuses into nuclei

!! Size of nuclei: depends upon atmosphere, mixer speed, shear forces!

Mixing!

!! Exposes dough components to oxygen!!! Enhances gluten development!

!!Oxygen changes weak SH bonds to strong SS bonds!!!Dough strengthener: L-Ascorbic acid (vitamin C)!

!! Ironically, not an oxidizing agent!!!! It must first be oxidized (to dehydroascorbic acid)!!! All vitamin C is volatilized during baking!

!! Oxidizes flavor elements!!!Carotenoid pigments => decreased flavor!

Mixing!

!! During mixing:!!! Water is absorbed:!

!!Minimally by starch (max = 20% of starch weight)!!!Maximally by proteins!

!! Proteins swell from entrapped water!

!! Water is dispersed, and serves as a fluid matrix in which dough activities occur!

Mixing!

!! During mixing:!!! Gluten development begins!

!!Air is entrapped in the developing gluten matrix!!!Starch is entrapped in the gluten matrix

surrounding entrapped air!!!Dough cohesiveness begins to occur!!!As gluten develops, dough s viscoelastic

properties change!

Mixing!!! Mixing intensity - !

!! Dough properties: water absorption - absorption increases with mixing intensity!

!! Dough texture: shear & elongation forces distribute and resize gas nuclei!

!! Degree of mixing -!!! Stage 1: end of homogenization - short dough!!! Stage 2: middle of mixing - coherence increases!!! Stage 3: strong coherence - window possible!!! Stage 4: sticky, extensible, soft - overmixing!

Mixing!!! Influence of mixing on final product!

!! Coherence increases with mixing!!! Result:!

!! Crumb softness and resiliency increases!!! Crust toughens!

!! Influence of temperature!!! Affects fermentation (10% change / 1°C)!!! Note: 8g ice/kg dough => temp drops 1°C!!! Affects gluten development - increased speed of

development with increased temperature!!! May affect moisture on surface of dough!

Fermentation!!! Process of fermentation:!

!! Begins as soon as yeast cells are hydrated!!! Begins aerobically, as yeast respire oxygen

that is entrapped in the dough!!! Aerobic metabolism ends almost immediately

after mixing ends; oxygen is rapidly exhausted from the gas nuclei!!!From that point, reproduction ceases!

Fermentation!!! Food supply!

!! Damaged starch granules quickly hydrate!!!Hydration:!

!! Expands granule size!!! Separates starch chains, one from the next!!! Leaves damaged starch subject to attack by amylases!

!! Enzyme activity:!!!Amylase breaks damaged starch down, principally to

maltose!!!Maltase breaks maltose down into two glucose

molecules!

Fermentation - no oxygen!Fermentation - no oxygen!! Formula:!

!! One molecule of glucose =>!!! 2 molecules of ethanol (ethyl alcohol)!!! 2 molecules of CO2

!! Fate of products:!!! Ethanol: enters liquid matrix, may combine with other

elements to produce flavor compounds !! CO2:

!! dissolves in water !! Diffuses into entrapped gas nuclei (now depleted of oxygen,

and containing only nitrogen from the atmosphere)

Fermentation!!! Bulk fermentation!

!! Purpose: Continue dough development!!!Mechanism: biaxial stretching due to gas

development => toughening of the dough!

!! Stretch & Fold / Punch down !!! Purpose: Increase gluten strength!

!!Mechanism: increase protein cross-linking!

!! Final Proof!!! Purpose: Increase specific volume!

!!Mechanism: gas production!

Fermentation!

!! Bulk fermentation!!! Begins with production of CO2 from respiration!!! CO2 is in a liquid phase in the space between gas

nuclei!!!Concentration increases during first ~30 minutes!

!! CO2 is in a gas phase within the gas nuclei!!!Commences almost immediately!!!Remains proportional to liquid-phase CO2

!! Force resisting gas cell expansion: surface tension, not dough viscosity!

Fermentation!

!! Gas Cells!!! Very stable: walls strengthen with stretching!!! Crumb: virtually no loss of CO2 from

membrane rupture, etc.!!! Surface: CO2 diffuses from dough into

atmosphere!!!This accounts for crust structure!!! If proofed in CO2-rich atmosphere, crust is

blistered and torn!

Fermentation!

!! Change in pH!!! Multiple acids are produced, including:!

!!Carbonic acid -- in all fermenting doughs; from CO2 and water!

!!Acetic acid -- sourdough!!!Lactic acid -- sourdough!

!! Acids are buffered by wheat proteins!!! pH yeast dough: 5.4 -- 5.7!!! pH sourdough: 4.0 -- 4.5!

Fermentation!!! Temperature changes during fermentation!

!! Heat is produced!!!12g sugar / kg dough => ~2.8°C /kg dough!

!! Condensation!!!1g moisture /kg dough => 1°C temperature increase!

!! Evaporation!!!1g moisture /kg dough => 1°C temperature decrease!

!! Air temperature!!!Heat capacity of air is 1.2 kJ/m3*°C!!!Specific heat of dough is 2.7kJ/kg*°C!!!Result: air temp plays minor role in dough temp!

Baking!

!! Baking produces massive physical changes!!! Dough (liquid) => crumb (solid)!!! Dough (foam) => crumb (sponge)!!! Dough (.8 liters/kg) => bread (up to 5 liters/kg)!

!! Baking produces massive chemical changes!!! Proteins give up water!!! Starch granules become hydrated!!! Maillard reaction occurs in the crust!

Baking!

!! Heat transfer!!! Radiation = transfer of heat by

electromagnetic waves from a source of heat!!! Convection = transfer of heat by movement of

a fluid away from a source of heat!!! Conduction = transfer of heat by molecular

agitation with the object, without overall movement of the object itself!

!! Condensation/Evaporation: heat transfer as a result of phase change!

Baking!

!! Radiation!!! Heat radiates from oven walls/deck/roof!

!!Electromagnetic radiation (between radio waves and visible light)!

!!Short- and Medium wave infrared wavelengths!!!These waves do not bend!!!Result: color differences may occur between top

and sides of the bread !!!Penetration: maximum = < 1/4 (~4 mm, max)!

Baking!!! Convection!

!! Cold object (dough) in oven => movement of air over the object and downward!

!! Air movement causes heating by convection!!! Without a fan, convection is minimal!!! At 1 m/s airflow, convection is about 1/3

total heat transfer!!! To prevent excessive crust browning from

forced convection, must lower oven temperature 20°C -- 30°C!

Baking!

!! Conduction!!! Very little through still air!!! Very high at the deck/dough interface!!! Because deck and dough have low conductivity,

the dough does not burn at its point of contact.!

Baking!

!! Condensation!!! With steam injection:!

!!Condensation on dough with steam injection => surface temperature of 80° C, instantaneously!

!! Gelatinizes starches, dissolves sugars!

!! Within dough:!!!Moisture evaporates from warmer side of gas cell,

travels across cell, and condenses on other side.!!!Moisture moves towards center of dough!!!The higher the specific volume of the dough, the

greater the contribution of evaporation/condensation!

Baking!

!! Crumb formation!!! Starch gelatinizes!

!!Swelling begins at about 55° C!!!Starch granules lose their orderly arrangement!!!Amylose leaks from the granules!

Baking!!! Effect of heat!

!! Initial increase in cell activity: initial increased rate of CO2 and ethanol production!

!! When temp >40°C, CO2 production declines!!! Increased rate of extra-cellular activity!

!!E.g. amylase!!! Proteins swollen with water, expel the water!!! Heat, in the presence of water, overcomes the

binding of one starch chain to the next in the granules!

Baking!

!! Effect of heat:!!! Temp < 40° C, gas production is largely from

cellular production of CO2!!! Temp > 40° C, gas production is from:!

!!CO2 dissolved in water changes to gas!!!Ethanol becomes a gas!

!! As temperature increases further!!!Loaf volume expands due to expanding gasses!!!Water becomes steam!

Baking!!! Effect of heat!

!!At about 150 °F, starch begins to hydrate!!!Separation of hydrated starch chains leaves

them subject to attack by amylases!!!Amylase in wheat flour is active to about 167 °F;

higher still in rye !!!Sugar results from the increased action of

amylase!!!Yeast cells have died from heat, so the sugar is

not metabolized!!!The resulting sugar softens and smooths the

crumb!

Baking!!! Effect of heat!

!! Starch hydration continues!!!Heated, starch holds water up to 10X its weight!!!Hydrated starch gelatinizes as temperature rises!!!Dough (foam with 100% gas retention) => sponge

(interconnected cells with no gas retention)!!!Rigid gas cell walls fracture!!!When cooled, gelatinized starch provides rigidity

to the crumb structure!

Baking!

!! Crust formation!!! With increasing heat, the crust loses its

moisture!!!Maillard reaction occurs!

!! Non-enzymatic browning caused by reaction of!!! Reducing sugars (glucose, fructose, maltose) and!!! Proteins (gluten, albumins, etc.)!

!! Dough = starch + glucose => no browning!!! Dough = starch + protein => no browning!!! Dough = starch + glucose + protein => browning!

Baking!

!! Crust formation and movement of moisture!!! Initially, moisture evaporates and diffuses to

interior of crumb.!!! As moisture moves to center, the crumb begins

to dry and become stiff!!! As interior crumb temperature increases,

moisture moves to exterior of loaf!!! Crust formation is time consuming: baguette

crumb at 100° C in ~ 7 min; baking time ~25 min.!

Baking!

!! Crust color is affected by crust composition:!!! Short fermentation => reddish, not golden-brown!!! Low protein => pale, not golden brown!!! Low sugar => light colored crust!!! Skinned dough => faint crust color!

!!Moisture is necessary in first five or more minutes for Maillard reaction!

Staling!!! Potential factors that have been examined:!

!! Amylopectin retrogradation, amylose, flour protein, water-insoluble pentosans; water-soluble pentosans, interaction of pentosans with proteins, pentosans and starch retrogradation, native lipids, storage temperature, moisture migration, crumb-crust moisture redistribution, moisture redistribution among other components, processing factors!

Staling!!! What can be said at this point:!

!! Complex phenomenon!!! Multiple mechanisms!

!!Polymer crystallization with!!! Primary cause: Retrogradation (recrystallization) of

amylopectin, associated with!!! Water distribution shifts, changing the nature of the

gluten network.!

!

Cooling!!! Temperatures:!

!! At oven removal: Crust 180° C; crumb 100° C!!! After a few minutes: Crust and crumb 100° C!!! Thereafter, crust temp < crumb temp!

!!Moisture from crumb evaporates; condenses in crust!!!Evaporating moisture in crumb lowers pressure!!!Atmospheric air enters crumb to raise pressure!

!! Note that forced convection cooling will allow more water retention in the crumb than free convection cooling, because of the difference in evaporation rates!